Re: [Xen-devel] [PATCH] Allow guest to register a secondary vcpu_time_info structure

["Jan Beulich" <JBeulich@xxxxxxxxxx>]

>>> Jeremy Fitzhardinge <jeremy@xxxxxxxx> 06.10.09 02:10 >>>
>-void update_vcpu_system_time(struct vcpu *v)
>+static void update_guest_time_info(struct vcpu *v, struct vcpu_time_info *u)
>+{
>+    struct vcpu_time_info info;
>+    u32 version;
>+
>+    if ( guest_handle_is_null(v->time_info_guest) )
>+        return;
>+
>+    if ( __copy_from_guest(&info, v->time_info_guest, 1) )
>+        return;

I'd suggest using __copy_field_from_guest() here to get just the
version member, after copying *u into info.

>+
>+    /*
>+     * Update the guest copy of the time info.  We need to make sure
>+     * we update the guest's version of the version number rather than
>+     * use a verbtim copy of the master one, because the guest may
>+     * update the version for its own purposes.
>+     */
>+    version = info.version;
>+    info = *u;
>+    info.version = (version + 2) & ~1;
>+
>+    __copy_to_guest(v->time_info_guest, &info, 1);
>+}

Jan


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